Numerous proteolytic enzymes are known in the art for use in the debridement of burn or ulcer eschar. These enzymes help heal the burn or ulcer by debriding, i.e. actually digesting, the necrotic tissue and thereby promoting the growth of healthy new skin.
Various wound dressings and skin matrices have also been disclosed in the art which dressings cover and protect the open burn or ulcer during healing. These materials may have medicaments which promote the healing of the burn or ulcer incorporated therein.
For example, Keith et al. in U.S. Pat. No. 4,492,685 disclose a protective skin matrix which may include an agent to help promote healing. The matrix comprises an aqueous based product which includes 2 to 20 percent glycerol, 4 to 30 percent polyvinyl alcohol (PVA), 2 to 20 percent polyvinylpyrrolidone (PVP) and water in a weight ratio to the glycerol of from 3:1 to 7:1.
Fischer et al. in U.S. Pat. No. 4,556,056 disclose a transparent fluid bandage consisting of a hydrophilic organic transparent gel swollen with an aqueous solution which can contain wound treatment agents.
The difficulty in using these protective dressings with a proteolytic enzyme for the treatment of burns is that the water contained in these materials activates the enzyme causing autolysis, which is the process in which the enzyme digests itself. Within a short time after preparing these materials, all that would remain would be enzyme fragments or inactivated enzymes.
Bolton et al. in U.S. Pat. No. 4,668,228 disclose a debriding tape comprising a surgical tape having an enzyme in dry powder form on the adhesive surface. When the tape is applied to a burn and adhered to the surrounding healthy skin, the enzyme is activated by the fluid from the burn and immediately released into the burn area. A disadvantage to the Bolton et al. debriding tape is the fact that the pure enzyme can also digest healthy tissue/mucous membranes if activated by water or saline solution. Therefore, extreme caution must be exercised during manufacturing and by the caregiver during treatment so as to avoid injury to healthy skin of the manufacturer or caregiver. Additionally, although the tape is adhered to dry surrounding healthy skin, the possibility exists that perspiration or fluid seepage could activate the enzyme in the area of the healthy skin of the patient and cause injury to same.
Schmitt in U.S. Pat. No. 3,983,209 discloses a method for treating burns utilizing the combination of a proteolytic enzyme in a dry material comprising a hydrophobic, bioerodible polymer of the formula ##STR1## This produces a sustained release of the enzyme over time and is therefore not desirable for debriding burns or ulcers requiring a treatment comprising an immediate release of the enzyme into the wound.